Low Power AC Sensing Circuit for Image Formers
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Solution Overview
Problem
Image forming apparatuses face challenges in sensing whether power is supplied with low power consumption, leading to unnecessary printing when external power is temporarily cut off and then restored, as existing methods like photo-couplers consume too much power.
Innovation Solution
A power supply device that includes an input unit for AC power, a converter to DC power, and a sensor with a transformer and resistor unit to sense AC power input with low power consumption, using a sensing signal that is electrically insulated and amplified, allowing the image forming apparatus to determine if AC power is present and cancel printing jobs accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photo-coupler is used to sense power supply status, then the sensing function is achieved, but power consumption increases to about 0.2 W
Solution Approach 1:
The patent replaces the photo-coupler (optical sensing system) with a voltage sensing circuit that directly detects AC power presence through electrical parameters. This substitution eliminates the need for optical conversion and bias current, achieving power consumption of 1 W or less while maintaining sensing capability.
Solution Approach 2:
The patent changes the sensing parameter from optical signal detection (requiring bias current) to voltage level detection. By monitoring voltage presence/absence directly from the AC power line through a high-impedance voltage divider circuit, the system achieves accurate power status sensing with minimal power consumption.
2Loss of energy
If power is not monitored accurately, then power consumption is low, but unnecessary printing occurs when power is temporarily cut off
Solution Approach 1:
The patent implements a feedback mechanism where the voltage sensing circuit continuously monitors AC power status and provides real-time signals to the controller. The controller uses this feedback to determine whether to execute or cancel printing jobs, ensuring reliable operation while maintaining low power consumption through selective circuit activation.
Solution Approach 2:
The patent performs preliminary detection of power status before initiating printing operations. By checking voltage presence in advance and storing detection results, the system prevents unnecessary printing jobs from starting when power is actually cut off, thereby avoiding energy waste while maintaining operational reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the image forming apparatus to sense power supply with low power consumption, preventing unnecessary printing and achieving power consumption of 1 W or less in standby mode, allowing users to stop printing jobs intentionally.
Implementation Method 1
a transformer to receive the AC power and to output a sensing signal having a level reduced more than a level of the AC power
Data Source
AI summary
Power supply device and an image forming apparatus having the power supply device are provided. The power supply device includes an input unit to input alternating current (AC) power, a converter to convert the input AC power to direct current (DC) power having a preset level and to output the DC power, and a sensor to be connected to the input unit in parallel and to sense whether the AC power has been input. The sensor includes a transformer to receive the AC power and to output a sensing signal having a level reduced more than a level of the AC power, and a resistor unit connected to the transformer in series so that a current of the AC power input into the transformer is lower than or equal to a preset current.